Imaging using magnetic resonance (MR) imaging has in recent years established itself as a substantial aid for examining objects, particularly in medical diagnostics. These days, even the generation of high-resolution whole-body images for use in medical diagnostics seems to be possible. To this end, MR records, for example, from different regions of an examination object can be generated and combined to form an overall image. Inhomogeneities in the B0 field or spatial variations of magnetic field gradients, for example in the read-out and/or slice direction, can lead to distortions in the MR records, in particular in the edge regions thereof, which make combining the MR records more difficult.
Both the use of MR scanners with a larger field of view (FOV), which are advantageous in terms of the time required to generate an MR record, and the use of MR scanners with shorter magnet designs, which are advantageous in avoiding the patient feeling constricted, can favor inhomogeneities in the B0 field and variations of magnetic field gradients and can make combining different MR records even more difficult.
The paper by Stefan A. Reinsberg et al., “A complete distortion correction for MR images: II. Rectification of static-field inhomogeneities by similarity-based profile mapping”, Phys. Med. Biol. 50 (2005), pp. 2651-2661 and EP 1 942 350 A1 propose decreasing distortions in MR records by recording two MR records of the same region of an examination object, with the polarity of the read-out gradient being reversed in the two MR records, and elastically registering one of the MR records against the other MR record. However, this method leads to increased expenditure of time since two MR records of the same region of an examination object have to be generated with differing polarity of the read-out gradient. Moreover, the registration is effected against an MR record as a reference image which can in turn be distorted itself.